Marsdenian Substage

Much of the Marsdenian comprises thick mudstones and siltstones, which are seldom honoured by a name of
their own and are often overlooked, since they are reduced to low lying, vegetated land by weathering and
erosion. There are eight cycles of rhythmic sedimentation in the Marsdenian, but only three or four of these
contain significant named sandstone units. These mostly form strong landscape features and have frequently
been used commercially. The Marsdenian begins at the widespread Bilinguites gracilis Marine Band
and ends at the Gastrioceras cancellatum Marine Band.

Redmires Flags (up to 15 m thick)
The Redmires Flags are locally developed, as might be expected, around the Redmires Dams, west of Sheffield.
They consist of fine- to coarse-grained massive and thinly-bedded sandstones (Fig. 1).
The thinly-bedded sandstones can indeed be split to produce flagstones for paving or roofing, but the
massive sandstones are more suited to wall building - a warning not to take the name of a rock unit too
literally!

Fig. 2: The waste heap from the drift mine at Ringinglow (closed 1912)

Fig. 3: Copperas House (Photo Graham Hogg, Attribution-ShareAlike 2.0 Generic). The remains of
the stone tanks where the ferrous sulphate liquor was concentrated can still be seen behind the ruined building

Ringinglow Coal
The Ringinglow Coal and its associated seat earth occur just above the top of the Chatsworth Grit to the west
of Sheffield and Barnsley. It is up to 1.5 m thick, including dirt bands, and was worked around Stanage Pole
and Oaken Clough as well as at Ringinglow, where there are former underground mine workings and "pudding holes", i.e. bell pits
(Fig. 2). Its high content of pyrite rendered it poor for household use, but it was burned locally
and was also transported into the Calver-Stoney Middleton area where it was used as fuel in lime kilns.
The pyrite featured in a locally important copperas (ferrous sulphate) industry at Ringinglow.
Copperas was used in the tanning and dyeing industries (Fig. 3). The mines were mainly
worked in the 18th and 19th centuries and Ringinglow Colliery
was the last to close, in 1912.

Fig. 4: Millstones from the Chatsworth Grit on Stanage Edge, awaiting a customer!

Fig. 5: Casts of tree stems in the Chatsworth Grit, Millstone Edge

Fig. 6: Cross-bedded Chatsworth Grit at Stanage Edge

Chatsworth Grit (25 to 60 m thick)
This is called the Huddersfield White Rock in the north of our region and was also formerly known as Rivelin
Grit near to Sheffield. The Chatsworth Grit is the "millstone grit" of school textbooks, since it was
extensively quarried for the manufacture of grinding stones for corn and paper mills, drinking troughs and
architectural stonework (Fig. 4). It consists of fine- to coarse-grained, massive and
cross-bedded sandstones, with minor interbedded mudstones and siltstones. Pebbly layers are frequent and
casts of large fragments of drifted trees are not uncommon (Fig. 5).
The Chatsworth Grit represents the culmination of an upwardly coarsening, prograding succession, i.e. it is a
delta-top deposit. Palaeocurrent directions mostly suggest a consistent flow of braided rivers, flowing
towards the south-west or west (Fig.6). Recent studies have identified a major incised palaeochannel
of regional significance in this unit (Waters et al, 2008)

Ashover Grit (up to 27 m thick)
The Ashover Grit becomes more important to the south of our area, but is only known from boreholes within
its boundaries.

Heyden Rock (up to 24 m thick)
This crops out in the north western parts of our area on Bradfield Moors, but thins out to nothing towards
the south. It consists of a massive coarse to medium-grained sandstone, becoming more flaggy nearer the top.